This application claims priority from Japanese patent application P2006-047010 filed Feb. 23, 2006. The entire content of the aforementioned application is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a safety switch for stopping driving of a machine such as a working robot when the switch senses opening of an opening/closing door for opening and closing a doorway of a working space in which the machine is disposed.
2. Description of the Related Art
There is a working space where a machine such as a working robot is fenced near its driving range to secure safety around the space. An opening/closing door of a doorway of such a working space is mounted with a safety switch for stopping the machine when the switch senses opening of the opening/closing door so as to secure safety of a worker who has entered the space.
As this type of safety switch, there is a conventional one in which an actuator is inserted into a safety switch main body to allow operation of a working robot when an opening/closing door is closed while the actuator is withdrawn away from the safety switch main body to stop the machine when the opening/closing door is opened, for example (refer to Japanese Patent Application Laid-Open No. 10-302580).
On the other hand, in order to prevent operation of the machine even if the opening/closing door is closed accidentally when the worker is remaining in the working space, there are developed safety switches in which an actuator is locked in a housed state so as not to protrude toward a safety switch main body so that the actuator cannot be inserted into the safety switch main body when the opening/closing door is merely closed.
As this type of safety switch, there is a conventional one including: an actuator provided to an opening/closing door; a safety switch main body having an insertion hole which is provided in such a position as to face the actuator and into which the actuator is inserted when the opening/closing door closes a doorway of a working space and an engaging means capable of being engaged with the actuator inserted into the insertion hole and structured so that the engaged state is cancelled when the engaged actuator moves to go out of the insertion hole; a closing piece for turning between a closing position for closing the insertion hole and an opening position for opening the insertion hole; and a locking mechanism (padlock) for locking the closing piece in the closing position (refer to Japanese Patent Application Laid-Open No. 2004-353849).
In this safety switch, if the insertion hole of the safety switch main body is closed with the closing piece, entry of the actuator into the safety switch main body is restricted. In this way, it is possible to prevent the actuator and the safety switch main body from becoming engaged to erroneously allow the machine to operate even when the opening/closing door is closed by mistake. By locking the locking mechanism, it is possible to reliably fix the closing piece in the closing position.
In the above-described prior-art safety switch, it is necessary to close the insertion hole of the safety switch main body with the closing piece so as to restrict entry of the actuator into the safety switch main body. Moreover, in order to reliably fix the closing piece in the closing position, locking is carried out by using the locking mechanism and the closing piece for turning between the closing position for closing the insertion hole and the opening position for opening the insertion hole and the locking mechanism (padlock) for locking the closing piece in the closing position are necessary. In a state in which the insertion hole is opened by the closing piece, the locking mechanism is carried around by the worker or stored in a proper storage space, which is inherently inconvenient since keeping and management of the locking mechanism are bothersome and the locking mechanism cannot be used because no one knows where it is stored or who is keeping it when it is actually necessary. Moreover, parts are many for the safety switch, which results in high cost.
With the above points in view, it is an object of the present invention to provide a safety switch which eliminates bothersome keeping and management of the locking mechanism and which requires fewer parts to reduce cost.